1. Field of the Invention
The present invention relates to a semiconductor integrated circuit and, more specifically, to a semiconductor integrated circuit and a method of manufacturing a semiconductor integrated circuit including a plurality of metal layers connected with a plurality of vias.
2. Description of the Related Art
With movement toward further miniaturization of a semiconductor integrated circuit, it has become more difficult to form wiring shapes for the connection of elements as designed. In particular, in an advanced semiconductor integrated circuit including a multi-layer interconnection, a terminal end of a wiring in one layer in the multi-layer interconnection is sometimes formed shorter than a predetermined shape, owing to an optical proximity effect (OPE) or the like. As a result, a phenomenon (shortening) occurs in which the wiring does not reach a position of a via hole, thereby causing a connection failure.
An increase of an aspect ratio of a via has also been advanced by the requirement for miniaturization of the wiring, and it has become more difficult to bury a via plug in the via hole. When the via is not formed at a desired position, reliability and yield of the circuit are decreased. Therefore, methods for decreasing a via defect and for improving the reliability and the yield have been examined.
To decrease occurrence of the shortening of the wiring, a wiring region in which the via is provided is preliminarily elongated or expanded. To improve low reliability owing to the via defect, upper and lower wiring layers are connected with two vias (double-cut vias) in place of one via (single-cut via).
However, in the multi-layer interconnection in which preferential directions of the wiring are set alternately in the vertical and horizontal directions, the wiring is extended in an orientation different from the preferential direction in each wiring layer in order to arrange the two vias connecting the upper and lower wiring layers to each other. Accordingly, another wiring pattern extending in the preferential direction cannot be disposed in the periphery of a portion to which the wiring is extended, so as to be adjacent thereto, and wiring efficiency is decreased.
In particular, in a design tool for designing the wiring by taking grids as references, the extended wiring portion is laid against the preferential direction, and thus grids in the preferential direction, in which it should have been possible to lay the wiring, are substantially occupied. Accordingly, the wiring efficiency is decreased. As a result, it becomes difficult to increase the density of the circuit, causing an increase of chip size.